Die bars are employed in manufacturing coated wire, such as insulated magnet wire. Die bars are generally rectangularly shaped, each having two sets of drilled passages: A first set drilled through the bar to receive wires threaded therethrough, and a second set to carry a liquid insulating material (such as an enamel, varnish or like coating material) from an application station terminal to each of a corresponding one of the first set of passages to coat the wires therein. If a single coat of insulating material is to be applied, the wire is pulled through the die bar where the wire is coated and then through an oven for curing. If the wire is to receive a number of coats of insulating material after the curing of the initial coat, the wire is pulled and guided around the oven to another of a corresponding number of application station terminals having a die bar appended thereto for further coating. Curing and coating then continue until the wire receives the desired number of coats.
During the start-up of a multicoat coating process, the wire is threaded through a series of die bars, each successive die bar having increasingly sized coating passages. The first die bar has the smallest passages for initially coating a bare wire threaded therethrough. Successive bars have increasingly larger passages for coating previously cured coated wire. The wire is threaded through all of the die bars prior to being threaded through the oven.
After threading the wire through all the die bars, the first die bar having the smallest passages is held at a first application station terminal. The wire and the other die bars are drawn through the oven by a rope tied to the die bars. The wire and other die bars are then directed around the oven to a second application station terminal where the die bar having the next larger passages is held to apply a second coating to the wire. The wire and other die bars are pulled through and around the oven, placing the die bars in subsequent application station terminals, until the die bar having the largest sized passages is held at a final application station terminal. The wire assumes a helical shape passing through a die bar, through and around the oven, through a second juxtaposed die bar, through and around the oven etc., until the wire is finally threaded through the oven. Once the wire is threaded, the application station terminals are activated to apply the plurality of coatings to the wire as the wire is pulled through and around the oven.
The prior art does not reveal an effective device for drawing the die bars through the oven. Current practice calls for kinking the wire above a first die bar to be threaded through the oven and behind the other die bars, and then tying a rope about the first die bar to pull the die bars and wire threaded therethrough through the oven. As the kinks will not pass through the die bar passages, the engagement of the wire kinks with the die bar causes the die bar to be supported and carried by the wire as the wire is drawn through the oven. However, the kinking must be removed (the wire straightened) prior to coating, to allow the wire to pass through the die bars passages. Such kinking and straightening weakens the wire, making it prone to breakage. Moreover, more delicate wire cannot suoport the weight of the die bar, engendering further breakage. The kinking also forces the wire to carry the die bars at odd angles risking snagging the wire and die bar in the oven or entry and exit openings thereof. Further, the wire may be laterally unrestrained as it passes through the oven, providing little or no impedance to harmonic or lateral motion that may develop in the wire, greatly increasing the probability that the die bar or wire may snag within the oven. If the wire is cured in vertical ovens, the wire must be kinked below the die bars to support the die bars while traveling up through the oven, and above the die bars for supporting the die bars while traveling back down the oven with the wire. Failure to kink the wire above the die bar, may permit the die bar to slide down the wire in an uncontrolled manner, thereby increasing the probability of breakage.
Accordingly, what is needed in the art is a carrier for supporting and pulling die bars through a curing oven without interference with, or breakage of the wire and without snagging the die bar in the oven or the entry or exit openings thereof.